<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 100px;
      height: 100px;
      border: 1px solid red;
      /*margin-left: 100px;
      margin-top: 100px;*/
      /*margin-bottom: 50px;*/
     /* display: inline;*/
    }
    #d2{
        width: 100px;
        height: 100px;
        border: 1px solid red;
        /*上下相邻彼此添加外边距 两者取最大值*/
        /*margin-top: 100px;*/
       /* display: inline;*/
       /* display: inline;*/
    }
    #s1{
        /*行内元素上下外边距无效*/
        margin-top: 100px;
        margin-right: 100px;
    }
    #s2{
        /*左右相邻彼此添加外边距 两者相加*/
        margin-left: 50px;
    }
    #big{
        width: 200px;
        height: 200px;
        background-color: green;
        overflow: hidden;
    }
    #big>div{
        width: 50px;
        height: 50px;
        background-color: red;
        margin-left: 50px;
        margin-top: 50px;
    }
    #border_div{
        width: 200px;
        height: 200px;
        border: 10px solid blue;
        border-radius: 110px;
    }
  </style>
</head>
<body>
<div id="border_div"></div>
<div id="big">
    <div></div>
</div>
<span id="s1">span1</span><span id="s2">span2</span>
<div id="d1">外边距测试</div>
<div id="d2">div2</div>
</body>
</html>